A replicated, randomized, controlled study in 2002–2004 in an irrigated maize field in southwest Spain found more water in soils with no tillage, compared to conventional tillage. Water availability: More water was found in soils with no tillage, compared to conventional tillage, in two of nine comparisons (0–10 cm depth, in 2004: 0.23–0.31 vs 0.14–0.19 cm3 water/cm3 soil). Methods: Conventional tillage or no tillage was used on four plots each (20 x 10 m plots). A mouldboard plough (0–30 cm depth, in October 2001–2003 and March and April 2002–2004) was used for conventional tillage, and maize residues were burned in September–October 2002–2004. Herbicide was used for no tillage (April and May–June 2002–2004), and maize residues were not burned.

A replicated, randomized, controlled study in 2002–2004 in an irrigated maize field in southwest Spain found less nitrogen and more microorganisms in soils with no tillage, compared to conventional tillage. Tillage had inconsistent effects on soil stability. Nutrients: Less nitrogen was found in soils with no tillage, compared to conventional tillage, in one of nine comparisons (0–5 cm depth, in 2002: 0.11 vs 0.12 g total N/kg soil). Soil erosion and aggregation: Lower stability was found in soils with no tillage, compared to conventional tillage, in two of nine comparisons (0–10 cm depth, in 2002: 31–35% vs 48–58% of aggregates were stable), but higher stability was found in two of nine comparisons (0–10 cm depth, in 2004: 61–69% vs 41–58%). Soil organisms: More microorganisms were found in soils with no tillage, compared to conventional tillage, in one of three years (0–5 cm depth, in 2004: 437 vs 261 colony forming units/g dry soil). Methods: Conventional tillage or no tillage was used on four plots each (20 x 10 m plots). A mouldboard plough (0–30 cm depth, in October 2001–2003 and March and April 2002–2004) was used for conventional tillage, and maize residues were burned in September–October 2002–2004. Herbicide was used for no tillage (April and May–June 2002–2004), and maize residues were not burned. For organic carbon, nitrogen, and aggregate stability, soil samples were collected in March, June, and October 2002–2004 (three samples/plot, 0–30 cm depth). For microorganisms, soils samples were collected every two months (0–5 cm depth). It was not clear whether these results were a direct effect of tillage or residue burning.

A replicated, randomized, controlled study in 2001–2004 in an irrigated maize field in southwest Spain found more water in soils with winter cover crops, compared to soils without winter cover crops. Water availability: More water was found in soils with short-term cover crops, compared to soils without cover crops, in one of nine comparisons (5–10 cm depth, in 2002: 0.33 vs 0.24 cm3 water/cm3 soil), and more water was also found in soils with long-term cover crops, compared to soils without cover crops, in five of nine comparisons (0.31–0.38 vs 0.24–0.30). Implementation options: More water was found in soils with long-term cover crops, compared to short-term cover crops, in six of nine comparisons (0.31–0.38 vs 0.25–0.30 cm3 water/cm3 soil). Methods: Cover crops (Avena strigosa lopsided oats) were sown on eight plots in September 2001–2003. Four of these plots had winter cover crops for six years before this (long-term cover crops), and four plots did not (short-term cover crops). Four other plots did not have winter cover crops from 2001–2004 or before. All plots were 20 x 10 m and were not tilled after 2001. Cover crops were suppressed with herbicide in April 2002–2004.

A replicated, randomized, controlled study in 2001–2004 in an irrigated maize field in southwest Spain found more organic matter, nitrogen, and microorganisms, and higher soil stability, in soils with winter cover crops, compared to soils without cover crops. Organic matter: Similar amounts of organic carbon were found in soils with short-term cover crops, compared to soils without cover crops (0–30 cm depth: 6–13 g C/kg soil), but more organic carbon was found in soils with long-term cover crops, compared to soils without cover crops, in eight of nine comparisons (8–32 vs 6–13). Nutrients: Similar amounts of nitrogen were found in soils with short-term cover crops, compared to soils without cover crops (0–30 cm depth: 0.07–0.15 g total N/kg soil), but more nitrogen was found in soils with long-term cover crops, compared to soils without cover crops, in eight of nine comparisons (0.08–0.25 vs 0.07–0.13). Soil erosion and aggregation: Higher soil stability was found in plots with short-term cover crops, compared to plots without cover crops, in two of nine comparisons (0–5 cm depth, in 2002–2003: 57%–79% vs 44–69% of aggregates were water-stable), and higher soil stability was also found in plots with long-term cover crops, compared to plots without cover crops, in eight of nine comparisons (57–88% vs 26–69%). Soil organisms: More microorganisms were found in soils with short-term cover crops, compared to soils without cover crops, in one of three years (2003: 662 vs 470 colony forming units/g dry soil), and more microorganisms were also found in soils with long-term cover crops, compared to soils without cover crops, in two of three years (576–694 vs 350–470). Implementation options: More organic carbon in eight of nine comparisons (8–32 vs 6–13 g C/kg soil), more nitrogen in seven of nine comparisons (0.08–0.23 vs 0.07–0.15 g total N/kg soil), higher stability in six of nine comparisons (58–75% vs 29–48% of aggregates were stable), and more microorganisms in one of three years (2002: 576 vs 389 colony forming units/g dry soil) were found in soils with long-term cover cropping, compared to short-term. Methods: Cover crops (Avena strigosa lopsided oats) were sown on eight plots in September 2001–2003. Four of these plots had winter cover crops for six years before this (long-term cover crops), and four plots did not (short-term cover crops). Four other plots did not have winter cover crops from 2001–2004 or before. All plots were 20 x 10 m. Cover crops were suppressed with herbicide in April 2002–2004. For organic carbon, nitrogen, and aggregate stability, soil samples were collected in March, June, and October 2002–2004 (three samples/plot, 0–30 cm depth). For microorganisms (bacteria and fungi), soils samples were collected every two months (0–5 cm depth).